Lithographic apparatus and in-line cleaning apparatus

ABSTRACT

A lithographic system includes an immersion type lithographic apparatus, which includes a support constructed and arranged to support a substrate, a projection system constructed and arranged to project a patterned beam of radiation onto a target portion of the substrate, a liquid confinement structure configured to at least partially fill a space between the projection system and at least one of the substrate and support with an immersion liquid, a liquid supply system arranged to provide the immersion liquid to the liquid confinement structure, and a cleaning liquid supply system arranged to provide a cleaning liquid to a surface of the lithographic apparatus that comes into contact with the immersion liquid. The system includes a switch to provide the cleaning liquid directly to the liquid confinement structure and to provide the immersion liquid indirectly to the liquid confinement structure via a liquid purification system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/549,037, filed on Jul. 13, 2012 and issued onMay 19, 2015 as U.S. Pat. No. 9,036,128, which is a divisionalapplication of U.S. patent application Ser. No. 12/318,037, filed onDec. 19, 2008 and issued on Aug. 14, 2012 as U.S. Pat. No. 8,243,255,which claims the benefit of priority from U.S. Provisional PatentApplication Ser. No. 61/008,299, filed on Dec. 20, 2007, the contents ofall of which are incorporated herein by reference in their entireties.

FIELD

The present invention relates to a lithographic apparatus and a methodfor removing or preventing contamination in a lithographic apparatus.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. The liquid is desirablydistilled water, although another liquid may be used. An embodiment ofthe present invention will be described with reference to liquid.However, another fluid may be suitable, particularly a wetting fluid, anincompressible fluid and/or a fluid with a higher refractive index thanair, desirably a higher refractive index than water, such as ahydrocarbon, such as a hydrofluorocarbon. The point of this is to enableimaging of smaller features since the exposure radiation will have ashorter wavelength in the liquid. (The effect of the liquid may also beregarded as increasing the effective numerical aperture (NA) of thesystem and also increasing the depth of focus.) Other immersion liquidshave been proposed, including water with solid particles (e.g. quartz)suspended therein. The particles may be of the size of nanoparticles,and may be provided in a concentration that increases the refractiveindex of the liquid in which they are suspended.

However, submersing the substrate or substrate and substrate table in abath of liquid (see, for example, U.S. Pat. No. 4,509,852, herebyincorporated in its entirety by reference) means that there is a largebody of liquid that must be accelerated during a scanning exposure. Thisrequires additional or more powerful motors and turbulence in the liquidmay lead to undesirable and unpredictable effects.

One of the solutions proposed is for a liquid supply system to provideliquid on only a localized area of the substrate and in between thefinal element of the projection system and the substrate using a liquidconfinement system (the substrate generally has a larger surface areathan the final element of the projection system). One way which has beenproposed to arrange for this is disclosed in PCT patent applicationpublication no. WO 99/49504, hereby incorporated in its entirety byreference. As illustrated in FIGS. 2 and 3, liquid is supplied by atleast one inlet IN onto the substrate, preferably along the direction ofmovement of the substrate relative to the final element, and is removedby at least one outlet OUT after having passed under the projectionsystem. That is, as the substrate is scanned beneath the element in a −Xdirection, liquid is supplied at the +X side of the element and taken upat the −X side. FIG. 2 shows the arrangement schematically in whichliquid is supplied via inlet IN and is taken up on the other side of theelement by outlet OUT which is connected to a low pressure source. Inthe illustration of FIG. 2 the liquid is supplied along the direction ofmovement of the substrate relative to the final element, though thisdoes not need to be the case. Various orientations and numbers of in-and out-lets positioned around the final element are possible, oneexample is illustrated in FIG. 3 in which four sets of an inlet with anoutlet on either side are provided in a regular pattern around the finalelement.

There is a need to address the issue of contamination in a lithographicapparatus, such as the contamination generated by removal of particlesof top-coat material, resist or both. There are different types ofcontamination and the degree to which the lithographic apparatus shouldbe cleaned and the type of cleaner that should be used may depend on thetype of contamination that is present. Current cleaning methodsgenerally do not allow for in-line cleaning, and accordingly theircompletion may cause significant down-time of the apparatus.

SUMMARY

According to an embodiment of the invention, there is provided animmersion type lithographic apparatus that includes an immersion systemconfigured to at least partially fill an immersion space with animmersion liquid. The apparatus also includes an indicator configured toindicate whether a part of the lithographic apparatus should be cleaned,and a cleaning liquid supply system configured to supply a cleaningliquid that includes a cleaner to the part of the lithographicapparatus. The cleaner is at least one of a plurality of differentcleaners. The or each cleaner or combination of cleaners is configuredto clean a different type and/or level of contamination in the part ofthe lithographic apparatus. The apparatus also includes a controllerconfigured to control which of the plurality of cleaners is provided tothe part of the lithographic apparatus, based on an indication receivedfrom the indicator.

According to an embodiment of the invention, there is provided anin-line cleaning cabinet for an immersion type lithographic apparatus.The in-line cleaning cabinet includes a fluid outlet constructed andarranged to provide a cleaning fluid to the immersion type lithographicapparatus. The cabinet also includes a plurality of cleaner supplydevices that are in fluid communication with the fluid outlet. Each ofthe cleaner supply devices is constructed and arranged to supply acleaner to the fluid outlet. The cabinet also includes a controllerconfigured to control the plurality of cleaner supply devices based on alevel and/or type of contamination within the immersion typelithographic apparatus so that the cleaning fluid includes at least oneof the cleaners.

According to an embodiment of the invention, there is provided a methodof cleaning an immersion type lithographic apparatus. The methodincludes sensing contamination within the immersion type lithographicapparatus. The method also includes selecting a cleaning mode from aplurality of cleaning modes in response to the sensing. The methodfurther includes providing a cleaner from a cleaning system to thecontaminated part of the immersion type lithographic apparatus based onthe selected cleaning mode.

According to an embodiment of the invention, there is provided a methodfor supplying a cleaning fluid from an in-line cleaning cabinet to animmersion type lithographic apparatus. The method includes supplying afirst cleaner to the in-line cleaning cabinet, and supplying a secondcleaner to the in-line cleaning cabinet, and detecting an amount and/ortype of contamination within the immersion type lithographic apparatus.The method also includes determining a ratio of the first cleaner andthe second cleaner to mix with a fluid carrier based on the detecting,and supplying a mixture of the fluid carrier and the first cleanerand/or the second cleaner to the immersion type lithographic apparatus.

According to an embodiment of the invention, there is provided animmersion type lithographic system. The system includes an immersiontype lithographic apparatus, a liquid supply system, and a cleaningsystem. The lithographic apparatus includes a support constructed andarranged to support a substrate, and a projection system constructed andarranged to project a patterned beam of radiation onto a target portionof the substrate. The lithographic apparatus also includes a liquidconfinement structure configured to at least partially fill a spacebetween the projection system and the substrate and/or support with aliquid. The liquid supply system is constructed and arranged to supplythe liquid to the liquid confinement structure. The cleaning system isconstructed and arranged to supply at least one cleaner to the immersiontype lithographic apparatus. The cleaning system is in fluidcommunication with the liquid supply system and the liquid confinementstructure.

According to an embodiment of the invention, there is provided animmersion type lithographic apparatus. The apparatus includes a supportconstructed and arranged to support a substrate, and a projection systemconstructed and arranged to project a patterned beam of radiation onto atarget portion of the substrate. The apparatus also includes animmersion system configured to at least partially fill a space betweenthe projection system and the substrate and/or support with a liquid.The apparatus further includes a contamination indicator constructed andarranged to generate a signal that initiates a cleaning sequenceconfigured to clean at least a part of the lithographic apparatus. Theapparatus also includes a cleaning liquid supply system that isconfigured to provide a cleaning liquid to the part of the lithographicapparatus, the cleaning liquid supply system comprising a plurality ofdifferent cleaners, each cleaner or combination of cleaners beingconfigured to clean a different type and/or level of contamination inthe part of the lithographic apparatus.

According to an embodiment of the invention, there is provided animmersion type lithographic apparatus that includes a supportconstructed and arranged to support a substrate, and a projection systemconstructed and arranged to project a patterned beam of radiation onto atarget portion of the substrate. The apparatus also includes animmersion system configured to at least partially fill a space betweenthe projection system and the substrate and/or support with an immersionliquid. The apparatus further includes a cleaning liquid supply systemconfigured to provide a cleaning liquid to a part of the lithographicapparatus, and a drain switch constructed and arranged to direct theimmersion liquid to a first drain, and the cleaning liquid to a seconddrain depending on whether the immersion liquid or the cleaning liquidis flowing out of the immersion system.

According to an embodiment of the invention, there is provided animmersion type lithographic apparatus that includes a supportconstructed and arranged to support a substrate. The apparatus alsoincludes a projection system constructed and arranged to project apatterned beam of radiation onto a target portion of the substrate. Theapparatus further includes an immersion system configured to at leastpartially fill a space between the projection system and the substrateand/or support with an immersion liquid. The apparatus also includes acleaning liquid supply system configured to provide a cleaning liquid toa part of the lithographic apparatus. A switch is constructed andarranged to direct the immersion liquid through a liquid purificationsystem and to direct the cleaning liquid to by-pass at least a portionof the purification system.

According to an embodiment of the invention, there is provided animmersion type lithographic apparatus that includes a supportconstructed and arranged to support a substrate. The apparatus alsoincludes a projection system constructed and arranged to project apatterned beam of radiation onto a target portion of the substrate. Theapparatus further includes an immersion system configured to at leastpartially fill a space between the projection system and the substrateand/or support with an immersion liquid. The apparatus also includes acleaning liquid supply system configured to provide a cleaning liquid toa part of the lithographic apparatus via a first conduit. A switch isconstructed and arranged to direct the immersion liquid directly to aliquid purification system via a second conduit that is separate fromthe first conduit and to direct the immersion liquid through thecleaning liquid supply system.

According to an embodiment of the invention, there is provided a methodof cleaning an immersion type lithographic apparatus. The methodincludes sensing contamination within the immersion type lithographicapparatus, and providing a cleaner from a cleaning system to theimmersion type lithographic apparatus. The method also includesbypassing at least a portion of a liquid purification system within thelithographic apparatus with the cleaner, and cleaning a part of theimmersion type lithographic apparatus with the cleaner.

As used herein, “cleaner” includes any type of fluid that is capable ofcleaning a surface. The term “fluid” includes a gas, a liquid or anycombination thereof, such as a humidified gas and a liquid that includesa dissolved gas, or any other flowing medium, such as a supercriticalfluid or a nematic phase liquid crystal. The term “cleaning fluid” asused herein refers to a combination of a cleaner, typically at a lowconcentration, with a carrier fluid. The term “cleaning liquid” as usedherein refers to a cleaner that has been combined with a fluid that ispredominately a liquid. The term “immersion fluid” and “immersionliquid” as used herein refers to the fluid through which a patternedbeam of radiation passes through during exposure of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts a further liquid supply system;

FIGS. 6a-c depict a liquid removal device;

FIG. 7 depicts a schematic of an immersion type lithographic systemaccording to an embodiment of the invention;

FIG. 8 depicts a schematic of a cleaning liquid supply system accordingto an embodiment of the invention;

FIG. 9 depicts a schematic of an immersion type lithographic systemaccording to an embodiment of the invention; and

FIG. 10 depicts a schematic of an immersion type lithographic systemaccording to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises: an illuminationsystem (illuminator) IL configured to condition a radiation beam B (e.g.UV radiation or DUV radiation); a support structure (e.g. a mask table)MT constructed to support a patterning device (e.g. a mask) MA andconnected to a first positioner PM configured to accurately position thepatterning device in accordance with certain parameters; a substratetable (e.g. a wafer table) WT constructed to hold a substrate (e.g. aresist-coated wafer) W and connected to a second positioner PWconfigured to accurately position the substrate in accordance withcertain parameters; and a projection system (e.g. a refractiveprojection lens system) PS configured to project a pattern imparted tothe radiation beam B by patterning device MA onto a target portion C(e.g. comprising one or more dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The patterning device support structure holds the patterning device in amanner that depends on the orientation of the patterning device, thedesign of the lithographic apparatus, and other conditions, such as forexample whether or not the patterning device is held in a vacuumenvironment. The patterning device support structure can use mechanical,vacuum, electrostatic or other clamping techniques to hold thepatterning device. The patterning device support structure may be aframe or a table, for example, which may be fixed or movable asrequired. The patterning device support structure may ensure that thepatterning device is at a desired position, for example with respect tothe projection system. Any use of the terms “reticle” or “mask” hereinmay be considered synonymous with the more general term “patterningdevice.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more patterning device supportstructures). In such “multiple stage” machines the additional tablesand/or support structures may be used in parallel, or preparatory stepsmay be carried out on one or more tables and/or support structures whileone or more other tables and/or support structures are being used forexposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may comprise an adjuster AM for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section.

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device. Having traversed the patterningdevice MA, the radiation beam B passes through the projection system PS,which focuses the beam onto a target portion C of the substrate W. Withthe aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the patterning device support structure MTmay be realized with the aid of a long-stroke module (coarsepositioning) and a short-stroke module (fine positioning), which formpart of the first positioner PM. Similarly, movement of the substratetable WT may be realized using a long-stroke module and a short-strokemodule, which form part of the second positioner PW. In the case of astepper (as opposed to a scanner) the patterning device supportstructure MT may be connected to a short-stroke actuator only, or may befixed. Patterning device MA and substrate W may be aligned usingpatterning device alignment marks M1, M2 and substrate alignment marksP1, P2. Although the substrate alignment marks as illustrated occupydedicated target portions, they may be located in spaces between targetportions (these are known as scribe-lane alignment marks). Similarly, insituations in which more than one die is provided on the patterningdevice MA, the patterning device alignment marks may be located betweenthe dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the patterning device support structure MT and thesubstrate table WT are kept essentially stationary, while an entirepattern imparted to the radiation beam is projected onto a targetportion C at one time (i.e. a single static exposure). The substratetable WT is then shifted in the X and/or Y direction so that a differenttarget portion C can be exposed. In step mode, the maximum size of theexposure field limits the size of the target portion C imaged in asingle static exposure.

2. In scan mode, the patterning device support structure MT and thesubstrate table WT are scanned synchronously while a pattern imparted tothe radiation beam is projected onto a target portion C (i.e. a singledynamic exposure). The velocity and direction of the substrate table WTrelative to the patterning device support structure MT may be determinedby the (de-)magnification and image reversal characteristics of theprojection system PS. In scan mode, the maximum size of the exposurefield limits the width (in the non-scanning direction) of the targetportion in a single dynamic exposure, whereas the length of the scanningmotion determines the height (in the scanning direction) of the targetportion.

3. In another mode, the patterning device support structure MT is keptessentially stationary holding a programmable patterning device, and thesubstrate table WT is moved or scanned while a pattern imparted to theradiation beam is projected onto a target portion C. In this mode,generally a pulsed radiation source is employed and the programmablepatterning device is updated as required after each movement of thesubstrate table WT or in between successive radiation pulses during ascan. This mode of operation can be readily applied to masklesslithography that utilizes programmable patterning device, such as aprogrammable mirror array of a type as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

An immersion lithography solution with a localized liquid supply systemIH is shown in FIG. 4. Liquid is supplied by two groove inlets IN oneither side of the projection system PL and is removed by a plurality ofdiscrete outlets OUT arranged radially outwardly of the inlets IN. Theinlets IN and OUT can be arranged in a plate with a hole in its centerand through which the beam of radiation is projected. Liquid is suppliedby one groove inlet IN on one side of the projection system PL andremoved by a plurality of discrete outlets OUT on the other side of theprojection system PL, causing a flow of a thin film of liquid betweenthe projection system PL and the substrate W. The choice of whichcombination of inlet IN and outlets OUT to use can depend on thedirection of movement of the substrate W (the other combination of inletIN and outlets OUT being inactive).

Another immersion lithography solution with a localized liquid supplysystem solution which has been proposed is to provide the liquid supplysystem with a liquid confinement structure (or so-called immersion hood)IH. The liquid confinement structure IH extends along at least a part ofa boundary of the space between the final element of the projectionsystem PS and the substrate table WT, as shown in FIG. 1. The liquidconfinement structure may be substantially stationary relative to aprojection system in the XY plane though there may be some relativemovement in the Z direction (in the direction of the optical axis). Aseal may be formed between the liquid confinement structure and thesurface of the substrate. In an embodiment, the seal is a contactlessseal such as a gas seal.

Referring to FIG. 5, liquid confinement structure 12 forms a contactlessseal to the substrate around the image field of the projection system PLso that liquid is confined to fill an immersion space or reservoir 11between the substrate surface and the final element of the projectionsystem. The reservoir 11 is at least partly formed by the liquidconfinement structure 12 positioned below and surrounding the finalelement of the projection system PL. Liquid is brought into the spacebelow the projection system and within the liquid confinement structure12. Liquid may be brought into the space and/or removed from the spaceby liquid port 13. The liquid confinement structure 12 extends a littleabove the final element of the projection system and the liquid levelrises above the final element so that a buffer of liquid is provided.The liquid confinement structure 12 has an inner periphery that at theupper end, in an embodiment, closely conforms to the shape of theprojection system or the final element thereof and may, e.g., be round.At the bottom, the inner periphery closely conforms to the shape of theimage field, e.g., rectangular though this may not be the case.

The liquid is confined in the reservoir by a gas seal 16 formed betweenthe bottom of the liquid confinement structure 12 and the surface of thesubstrate W. The gas seal is formed by gas, e.g. air or synthetic air orN₂ or an inert gas. The gas is provided under pressure via inlet 15 tothe gap between liquid confinement structure 12 and substrate. The gasis extracted via outlet 14. The overpressure on the gas inlet 15, vacuumlevel on the outlet 14 and geometry of the gap are specificallyarranged. Desirably, the arrangement provides a high-velocity gas flowinwards that confines the liquid. The inlet and/or outlet may be annulargrooves which surround the space 11. The groove may be continuous ordiscontinuous. Such a system is disclosed in United States PatentApplication Publication No. US 2004-0207824.

In European Patent Application Publication No. EP 1,420,300 and UnitedStates Patent Application Publication No. US 2004-0136494, each herebyincorporated in their entirety by reference, the idea of a twin or dualstage immersion lithography apparatus is disclosed. Such an apparatus isprovided with two tables for supporting a substrate. Levelingmeasurements are carried out with a table at a first position, withoutimmersion liquid, and exposure is carried out with a table at a secondposition, where immersion liquid is present. Alternatively, theapparatus has only one table.

FIGS. 6a and 6b , the latter of which is an enlarged view of part of theformer, illustrate a liquid removal device 20 which may be used in animmersion system to remove liquid between the immersion hood IH and thesubstrate W. The liquid removal device 20 comprises a chamber which ismaintained at a slight underpressure p_(c) and is filled with theimmersion liquid. The lower surface of the chamber is formed of a porousmember 21. The porous member 21 may be a perforated plate or a thinplate having a large number of small holes, e.g. of diameter d_(hole) inthe range of 5 μm to 50 μm. The lower surface is maintained at a gapheight h_(gap) of less than 1 mm, desirably in the range of 50 μm to 300μm, above a surface from which liquid is to be removed, e.g. the surfaceof a substrate W. In an embodiment, porous member 21 is at leastslightly liquidphilic, i.e., for water, hydrophilic, having a contactangle of less than 90° to the immersion liquid, e.g. water.

The underpressure p_(c) is such that the menisci 22 formed in the holesin the porous member 21 substantially prevent gas being drawn into thechamber of the liquid removal device. However, when the porous member 21comes into contact with liquid on the surface W there is no meniscus torestrict flow and the liquid can flow freely into the chamber of theliquid removal device. Such a device can remove most of the liquid fromthe surface of a substrate W, though a thin film of liquid may remain,as shown in the drawings.

To improve or maximize liquid removal, the porous member 21 should be asthin as possible. The pressure differential between the pressure in theliquid p_(gap) and the pressure in the chamber p_(c) should be as highas possible. The pressure differential between p_(c) and the pressure ofthe gas in the gap p_(air) should be low enough to prevent a significantamount of gas from being drawn into the liquid removal device 20. It maynot always be possible to prevent gas being drawn into the liquidremoval device but the porous member will prevent large uneven flowsthat may cause vibration. A micro-sieve made by electroforming,photo-etching and/or laser cutting can be used as the porous member 21.A suitable sieve is made by Stork Veco B.V., of Eerbeek, theNetherlands. Other porous plates or solid blocks of porous material maybe used. However the pore size should be suitable to maintain a meniscuswith the pressure differential that will be experienced in use.

Such a liquid removal device can be incorporated into many types ofliquid confinement structure 12. One example is illustrated in FIG. 6cas disclosed in United States Patent Application Publication No. US2006-0038968. FIG. 6c is a cross-sectional view of one side of theliquid confinement structure 12, which forms a ring (as used herein, aring may be circular, rectangular or any other shape) at least partiallyaround the exposure field of the projection system PS (not shown in FIG.6c ). In this embodiment, the liquid removal device 20 is formed by aring-shaped chamber 31 near the innermost edge of the underside of theliquid confinement structure 12. The lower surface of the chamber 31 isformed by a porous member 30, as described above. Ring-shaped chamber 31is connected to a suitable pump or pumps to remove liquid from thechamber and/or maintain the desired underpressure. In use, the chamber31 is full of liquid but is shown empty here for clarity.

Outward of the ring-shaped chamber 31 are a gas extraction ring 32 and agas supply ring 33. The gas supply ring 33 has a narrow slit, which maybe continuous or discontinuous, in its lower part and is supplied withgas, e.g. air, artificial air or flushing gas, at a pressure such thatthe gas escaping out of the slit forms a gas knife 34. The gas formingthe gas knife is extracted by a suitable underpressure, which may beprovided by a vacuum pump connected to the gas extraction ring 32. Theresulting gas flow drives residual liquid inwardly where it can beremoved by the liquid removal device and/or the vacuum pump, whichshould be able to tolerate vapor of the immersion liquid and/or smallliquid droplets. However, since the majority of the liquid is removed bythe liquid removal device 20, the small amount of liquid removed via thevacuum system does not cause an unstable flow which may lead tovibration.

While the chamber 31, gas extraction ring 32, gas supply ring 33 andother rings are described as rings herein, it is not necessary that theysurround the exposure field or be complete. In an embodiment, suchinlet(s) and outlet(s) may simply be circular, rectangular or other typeof elements extending partially along one or more sides of the exposurefield, such as for example, shown in FIGS. 2, 3 and 4.

In the apparatus shown in FIG. 6c , most of the gas that forms the gasknife is extracted via gas extraction ring 32. Some gas may flow intothe environment around the immersion hood and potentially disturb theinterferometric position measuring system IF. This can be prevented bythe provision of an additional gas extraction ring outside the gasknife.

Further examples of how such a single phase extractor can be used in animmersion hood or liquid confinement system or liquid supply system canbe found, for example in European Patent Application Publication No.1,628,163 and United States Patent Application Publication No.2006-0158627. In most applications the porous member will be on anunderside of the liquid supply system. The maximum speed at which thesubstrate W can move under the projection system PS is in at least partdetermined by the efficiency of removal of liquid through the porousmember 21. One difficulty is that some of the holes may become blockedby debris, such as resist which has detached from a substrate duringimaging. This may reduce the maximum speed at which the substrate and/orsubstrate table can be moved without leaking of liquid from the liquidsupply system or liquid confinement structure.

The embodiment of the liquid confinement structure described above andillustrated in the Figures is provided as an example and is not intendedto be limiting in any way. For example, the liquid confinement systemmay include features disclosed in United States Patent ApplicationPublication No. 2007-0268466, such as embodiments of the gas knifeand/or the liquid extractor.

With reference to FIG. 1, the lithographic apparatus 1 of an embodimentof the invention comprises an immersion system having an immersion spacedefined by the substrate table WT or, when present the substrate W, theliquid confinement structure IH and the projection system PS.Contamination of one or more of the surfaces that come into contact withthe immersion fluid, such as a surface of the liquid confinementstructure IH, the projection system PS, and/or the substrate table WT,may build up over time if not removed.

FIG. 7 illustrates an embodiment of an immersion type lithographicsystem 100 that includes the lithographic apparatus 1 of FIG. 1, as wellas a cleaning liquid supply system 200. The immersion type lithographicsystem 100 may also include an immersion liquid supply system 300. Acleaning liquid may be supplied by the cleaning liquid supply system 200to a surface of the lithographic apparatus that comes into contact withthe immersion fluid. The cleaning liquid may help prevent the build upof contamination, and/or to remove contamination present on such asurface.

The lithographic apparatus 1 may include a contamination indicator CI.The contamination indicator CI may be used to provide an indication thatcleaning is desired. For example, the contamination indicator CI mayinclude a counter that counts the number of substrates that have beenexposed in the lithographic apparatus 1 since the previous cleaningaction. The contamination indicator CI may be configured to provide asignal to a controller 140 that is part of the lithographic apparatuswhen a certain number of substrates have been exposed. The certainnumber may be determined based on empirical data or may be determinedbased on a predicted level of contamination based on the type ofmaterials that come into contact with the immersion fluid. In anembodiment, the contamination indicator CI may be configured to keeptrack of the time that has elapsed since the previous cleaning action.The contamination indicator CI may provide a signal to the controller140 after a certain amount of time has elapsed. In an embodiment, thecontamination indicator CI is part of the controller 140.

The contamination indicator CI may alternatively or additionally be incommunication with one or more sensors S located within or near thelithographic apparatus that are configured to detect the amount and/ortype of contamination. The sensor S may be located in or on the liquidconfinement structure. In an embodiment, the sensor S may be an in-lineparticle counter that is configured to count contamination particles inthe immersion fluid. The contamination indicator CI may be configured toprovide long-term trend analysis of measurements made by the in-lineparticle counter. The contamination indicator CI may provide a signalwhen a certain, pre-determined level of particles has been reached. Thesignal may be provided once the level of particles has been detected fora certain, predetermined duration of time. One or more other sensorswithin the lithographic apparatus may be used to trigger thecontamination indicator to provide a signal to the controller so that acleaning action may commence. For example, temperature measurement ofthe liquid confinement structure may be monitored for an indication thatliquid containment performance of the liquid confinement structure hasdeteriorated due to contamination. Such a sensor is described in U.S.Provisional Patent Application No. 60/960,386, filed Sep. 27, 2007,which is incorporated herein by reference in its entirety.

The immersion liquid supply system 300 may include various componentsthat are constructed and arranged to prepare the immersion liquid foruse in the lithographic apparatus 1. In an embodiment, the immersionliquid may be ultra pure water, and the immersion liquid supply system300 may include one or more various filters that may be used to improvethe purity of the water being supplied to the immersion liquid supplysystem 300. In an embodiment, the immersion liquid supply system 300 maybe contained within a single point-of-use cabinet 302.

As illustrated in FIG. 7, the immersion liquid supply system 300 is influid communication with the cleaning liquid supply system 200 and thecleaning liquid supply system 200 is in fluid communication with thelithographic apparatus 1. In an embodiment, the immersion liquid supplysystem 300 may be in direct fluid communication with the lithographicapparatus 1 such that the liquid that flows out of the immersion liquidsupply system 300 bypasses the cleaning liquid supply system 200. Theimmersion liquid supply system 300 may be located within an enclosurethat also encloses the cleaning liquid supply system 200. The cleaningliquid supply system 200 may be located within an enclosure that alsoencloses the lithographic apparatus 1. In an embodiment, the immersionlithographic system 100 may be enclosed within a single enclosure.

FIG. 8 illustrates an embodiment of the cleaning liquid supply system200 in greater detail. As illustrated, the cleaning liquid supply system200 includes a single point-of-use cabinet 202, an inlet 210, an outlet212, and a conduit 214 that connects the inlet 210 to the outlet 212.The word “conduit” as used herein may have any configuration that issuitable to convey a fluid from one location to another location, andshould not be considered to be limiting in any way. The inlet 210 is influid communication with the immersion liquid supply system 300, and theoutlet is in fluid communication with the lithographic apparatus 1. Thecleaning liquid supply system 200 includes a plurality of cleanersources or supplies 220, 222, 224. Although three cleaner sources areillustrated in FIG. 8, more or less cleaner sources may be included inthe cleaning liquid supply system 200. Each of the cleaner sources 220,222, 224 in FIG. 8 may be provided to the cleaning liquid supply system200 in a container or may be provided from an external source via aconduit. The boxes representing the cleaner sources 220, 222, 224schematically depict the sources of cleaner, whether in the form of anactual container, or in the form of a connection to a larger supply.

For each of the cleaner sources 220, 222, 224, a cleaner supply device226, 228, 230 may be provided in a respective conduit that connects thecleaner sources 220, 222, 224 to the conduit 214 via a mixer 232. Thecleaner supply devices 226, 228, 230 are configured provide therespective cleaner to the mixer 232 at a certain flow rate and/or for acertain duration of time. The flow rate and/or duration of time may bedependent on the type of cleaning and the duration of cleaning thatshould be conducted within the lithographic apparatus. The cleanersupply devices 226, 228, 230 may each include a pump, valve, or anyother type of device that may be used to control the flow of therespective cleaner from the respective cleaner source 220, 222, 224. Inan embodiment, at least one of the cleaner supply devices may include amass flow controller that is used in combination with a pressurizedsupply container that is pressurized with a gas such as nitrogen.

The cleaning liquid supply system 200 may include a controller 240. Thecontroller 240 is in communication with a controller 140 that is partof, or associated with, the lithographic apparatus 1, as shown in FIG.7. As discussed above, when the contamination indicator CI indicatesthat contamination is present or cleaning is otherwise desired, a signalmay be sent to the controller 140. The controller 140 may then send asignal to the controller 240 to indicate that a particular type ofcleaning should be conducted. In an embodiment, the contaminationindicator CI may be in direct communication with the controller 240. Thecontroller 240 is in communication with the cleaner supply devices 226,228, 230, as shown in FIG. 8, and may be configured to control operationof the cleaner supply devices 226, 228, 230 in accordance with the typeof cleaning that is desired in the lithographic apparatus 1, asdescribed in further detail below.

The cleaning liquid supply system 200 may include a flow control device250 that is constructed and arranged to control the flow of the liquidentering the inlet 210 and whether the liquid entering the inlet 210flows into the mixer 232 or bypasses the mixer 232 via a bypass 216. Theflow control device 250 may include a three-way valve, a pump, or anyother device that may control the amount and/or direction of flow of theliquid entering the cleaning liquid supply system 200. The flow controldevice 250 may be in signal communication with the controller 240 sothat the controller 240 may control the flow of the liquid entering thecleaning liquid supply system 200. For example, if the lithographicapparatus 1 is to operate under exposure conditions, the controller 240may provide a signal to the flow control device 250 so that the mixer232 may be bypassed and the liquid may be provided to the lithographicapparatus 1 without any cleaner mixed therein. In an embodiment, nobypass may be provided and the liquid entering the cleaning liquidsupply system 200 may flow through the mixer 232 when no cleaner isbeing provided to the mixer 232.

The arrangement of the cleaning liquid supply system 200 may allowdifferent modes of cleaning to take place within the lithographicapparatus 1, particularly in a location where the immersion fluid comesinto contact with a part of the lithographic apparatus, such as theliquid confinement structure, the projection system, and/or thesubstrate table. For example, a cleaning mode may be configured for asituation where a light or less-aggressive cleaning should take place.Such a cleaning mode may be suitable for routine cleaning after acertain number of substrate exposures or after a certain time of use,even if minimal or no contamination has been specifically detected by acontamination sensor within the lithographic apparatus. Another cleaningmode may be configured for a situation where more aggressive cleaning isdesired, such as when a sensor has detected contamination within thelithographic apparatus. Additional cleaning modes that are based onspecific pre-determined cleaning needs may be provided. The controller240 may be pre-programmed with the different cleaning modes, and beconfigured to activate one or more of the appropriate cleaning supplydevices 226, 228, 230, depending on which cleaning mode is desired. Inan embodiment, the controller 240 may be reprogrammed or be programmableby a user.

The system may include a user interface 204 that is configured to allowa user to initiate a cleaning mode even if the contamination indicatorCI has not provided a signal to initiate cleaning. The user interface204 may include a display that is configured to provide the user withinformation being provided to the controllers 140, 240 by thecontamination indication CI and/or the sensor S. The user interface 204may be in signal communication with the controller 140 so that if acleaning mode is initiated by the user, proper precautions may be takenwithin the lithographic apparatus 1 prior to the start of the cleaningmode. The controller 140 then signals the controller 240 to start thecleaning mode when the lithographic apparatus 1 is ready to receive thecleaning liquid. This may give the system added flexibility so that ifan off-line contamination detection method indicates that there may becontamination within the lithographic apparatus, the user may initiate acleaning cycle.

The cleaner provided by the cleaner source 220 may consist of or consistessentially of a water-soluble cleaning component, such as a componentmade up of the elements hydrogen H and oxygen O, such as hydrogenperoxide, H₂O₂. This material has an effective cleaning action to removecontamination, and yet there is a reduced likelihood of damage beingcaused to the apparatus. Cleaning with hydrogen peroxide is particularlyeffective for removing flakes or other particles originating from theorganic process layers present on a substrate, e.g. resist and topcoat.Hydrogen peroxide is also a relatively safe and simple material tohandle and is less corrosive to component surfaces than other moreoxidizing materials. Suitable concentrations of hydrogen peroxide whenused alone are up to 10%, in an embodiment from 0.1% to 5%. Typically,the concentration that may be used is 2.5%.

The cleaner provided by the cleaning source 222 may consist of orconsist essentially of ozone, O₃. In an embodiment, the cleaning liquidprovided to the lithographic apparatus contains ozone. The ozone may begenerated in-situ as described in, for example, U.S. Patent ApplicationNo. 60/935,037, filed on Jul. 24, 2007, which is incorporated herein byreference in its entirety, or an external ozone source may be used.Concentrations of ozone may be selected from 1 ppm to 50 ppm, forexample selected from 1 ppm to 20 ppm, or selected selected from 1 ppmto 10 ppm.

In an embodiment, the cleaning liquid may consist of or consistessentially of ultra-pure water containing hydrogen peroxide fromcleaning source 220 and ozone from cleaning source 222, which creates acleaner commonly known as peroxone. For example, if the controller 240determines that a more aggressive cleaning mode should be used to cleanthe lithographic apparatus, the controller 240 may signal the one ormore cleaner supply devices 226, 228, 230 to provide suitable amounts ofthe respective cleaners from the cleaning sources 220, 222, 224 to themixer. For example, the combination of hydrogen peroxide and ozone is areactive mixture which will in part spontaneously react to produce thehighly oxidizing species OH (hydroxyl radical). This combination isadvantageous since the OH radical can be produced without theapplication of UV radiation. All wetted surfaces of the immersion spacemay therefore be cleaned, and cleaning is not limited to a surface whichcan be exposed to UV radiation. Cleaning with peroxone is effective formany types of contamination which can be difficult to remove with aweaker cleaning agent, such as oxygen, ozone, and hydrogen peroxide.

Typical concentrations of ozone in the cleaning liquid are selected from0.1 ppm to 20 ppm, for example at least 1 ppm, 2 ppm or at least 5 ppm.The concentration of ozone may be typically 15 ppm or 12 ppm. About 10ppm is desirable. Typical concentrations of hydrogen peroxide in thecleaning liquid are selected from 0.1 ppm to 10 ppm, for example atleast 0.5 ppm or at least 1 ppm. The concentration of hydrogen peroxidemay be typically 8 ppm or 5 ppm. About 2 ppm hydrogen peroxide isdesirable. The peroxone mixture may be more effective when used with aratio by concentration of hydrogen peroxide to ozone of 0.2:1 to 0.5:1.In an embodiment, the concentrations of the components of the mixturemay be 2.5 ppm hydrogen peroxide and 10 ppm ozone.

In an embodiment, at least one of the cleaner sources 220, 222, 224 mayinclude another cleaner, such as a detergent, soap, an acid, analkaline, or a solvent, such as a non-polar organic solvent or a polarorganic solvent, or any other suitable cleaner for the lithographicapparatus. For example, the cleaner may include diethylene glycolmonobutyl ether and/or ethoxylated secondary C12-14-alcohol, e.g.aldyloxypolyethyleneoxyethanol. In an embodiment, the cleaner may be amixture of water, diethylene glycol monobutyl ether, and ethoxylatedsecondary C12-14-alcohol, such as TLDR-A001 or TLDR-A001-C4, which aremanufactured by Tokyo Ohko Kogyo Co., Ltd. The controller 240 may beprogrammed to provide such a cleaner in another cleaning mode, which maybe defined by the user.

In an embodiment, the cleaner may include water, a solvent selected fromone or more glycol ethers, esters, alcohols and ketones, and asurfactant. In an embodiment, the water is clean, for example the watermay be ultra-pure water. The solvent should be chosen to have areasonable match with the contamination that is to be removed. This canbe determined, for example, using the Hansen theory (see, for example,Hansen Solubility Parameters, Charles M. Hansen, 2^(nd) edition, CRCpress, ISBN 0-8493-7248). Typically, the solvent will have a match,determined using the Hansen theory, of at least 50% (i.e. it will bepositioned near the center of the Hansen solubility sphere). The solventused will also in general be completely mixable in water. In anembodiment, the solvent may have a solubility of more than 10 wt % inwater. In an embodiment, the solvent may have a flash point above 38°C., for example above 70° C. or above 93° C.

Glycol ethers for use in the cleaning fluid may include propyleneglycolethers, such as propylene glycol methyl ether (PGME), dipropyleneglycol methyl ether (DPGME), tripropylene glycol methyl ether (TPGME),propylene glycol ethyl ether (PGEE), propylene glycol normal propylether (PGPE), dipropylene glycol normal propyl ether (DPGPE), propyleneglycol normal butyl ether (PGBE), dipropylene glycol normal butyl ether(DPGBE), tripropylene glycol normal butyl ether (TPGBE) and propyleneglycol tertiary butyl ether (PGTBE); ethylene glycolethers, such asdiethylene glycol methyl ether (DEGME), diethylene glycol ethyl ether(DEGEE), diethylene glycolpropyl ether (DEGPE), ethylene glycol butylether (EGBE) and diethylene glycol butyl ether (DEGBE); propylene glycolether acetates, such as propylene glycol methyl ether acetate (PGMEA)and dipropylene glycol methyl ether acetate (DPGMEA), and ethyleneglycol ether acetates, such as ethylene glycol butyl ether acetate(EGBEA) and diethylene glycol butyl ether acetate (DEGEA). In anembodiment, the glycol ether may be selected from DEGBE, DEGPE, PGME andDPGME. In an embodiment, the glycol ether is DEGBE.

Esters for use in the cleaning fluid may include compounds which have anester functionality. Suitable compounds include methyl lactate, ethyllactate, propyl lactate, butyl lactate, gamma butyrolactone, methylacetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate,t-butyl acetate and gamma butyrol acetate. In an embodiment, the esteris a dibasic ester. In an embodiment, the ester is ethyl lactate orbutyrolactate.

Ketones for use in the cleaning fluid may include cyclohexanone ordiacetone alcohol.

Alcohols for use in the cleaning fluid may include methanol, ethanol,propanol, such as isopropanol, t-butyl alcohol, 4-methyl-2-pentanol andcyclohexanol.

In an embodiment, the solvent is selected from one or more glycol ethersor esters. In one embodiment, the solvent is selected from one or moreglycol ethers.

In an embodiment, the solvent is selected from DEGBE or ethyl lactate.In an embodiment, the solvent is DEGBE.

In an embodiment, the surfactant is selected from one or more nonionic,cationic or anionic surfactants. In an embodiment, the surfactant isselected from one or more nonionic surfactants. In an embodiment, thesurfactant comprises a nonionic surfactant which is an ethyleneoxide/propylene oxide block copolymer with a molecular weight from 1000to 3000. A suitable such surfactant is Pluronic® L61 from BASF. In anembodiment, the surfactant comprises a defoaming wetting agent such asEnvirogen® AD01 from Air Products.

In an embodiment, the cleaning fluid further comprises a pH adjustmentchemical. If present, the pH adjustment can be used to ensure that thepH of the cleaning fluid is from 7 to 10, for example from 8 to 10 orfrom 9 to 10. Suitable pH adjustment chemicals may include inorganicbases such as sodium hydroxide, potassium hydroxide or a phosphatebuffer. Increasing the pH of the solution can decrease the adhesiveforces between the contaminant and the surface and may therefore resultin more efficient cleaning. However, increasing the pH beyond 10 shouldin general be avoided since this may lead to damage to parts of thelithographic apparatus, for example the lens.

In an embodiment, the cleaning fluid may be free from nitrogencontaining compounds. In an embodiment, the cleaning fluid may be freefrom ammonia and amines. These compounds are volatile alkalines and mayadversely affect the processing of the photo resist.

In an embodiment, at least one of the cleaner sources may includeoxygen. The concentration of oxygen in the cleaning liquid may be up to10 ppm, for example up to 5 ppm or up to 2 ppm. The maximum oxygenconcentration is the maximum oxygen saturation using atmospheric air. Agas mixture enriched with oxygen may be used, which may achieve a highersaturation level. Using an oxygen enriched gas mixture, a concentrationof up to 50 ppm may be achieved. The use of oxygen as the cleaner may behighly beneficial from a safety point of view. Further, oxygen can beactivated into more oxidizing cleaning species such as ozone in-situ, byapplication of UV radiation. Consequently, effective cleaning may beachieved, including the removal of contaminants such as partlycarbonized materials which can be difficult to remove with knowncleaning agents.

In an embodiment, the cleaning power of a cleaning liquid of anembodiment of the invention may be increased by UV irradiation of thecleaning liquid. In the case of a cleaning liquid which containsultra-pure water and oxygen, such irradiation is particularly desiredsince this will generate ozone in situ in the immersion space. The ozonemay be further activated in the lithographic apparatus to provide highlyoxidizing species such as the OH radical. In an embodiment in which thecleaning liquid contains hydrogen peroxide and/or ozone, cleaning ishighly effective without irradiation. However, UV irradiation mayenable, or increase, the formation of the highly reactive OH radical andthereby provide improved cleaning effect. For example, the presence ofthe OH species will provide improved cleaning of carbonized or partlycarbonized contaminants in the immersion space.

The UV radiation used may be provided by the projection system of theapparatus, or by a separate UV radiation source such as a low pressureHg lamp or an excimer laser. An appropriate wavelength is typicallyabout or less than 250 nm. Where ozone is present in the cleaningliquid, a wavelength of less than 220 nm is desired since a wavelengthof greater than 220 nm will induce breakdown of ozone to oxygen. In anembodiment, 193 nm wavelength radiation may be used.

For embodiments in which UV radiation should not be used in combinationwith the cleaner, the controller 240 may be configured to provide asignal to the controller 140 of the lithographic apparatus indicatingthat the cleaner is about to be supplied to the lithographic apparatus.In response, the controller 140 may turn off the radiation source or mayotherwise prevent the radiation from reaching the cleaning liquid as thecleaning liquid flows through the lithographic apparatus.

The cleaning liquid exiting the cleaning liquid supply system 200 viathe outlet 212 may be supplied to the immersion space, for example byflushing the cleaning liquid through the lithographic apparatus. Thecleaning liquid may be supplied to the immersion space using the sameinlet system as the immersion liquid, for example inlet IN as depictedFIGS. 2, 3 and 4 or inlet 13 of FIG. 5. In an embodiment, the cleaningliquid may be supplied to a dedicated cleaning station located withinthe lithographic apparatus, such as on the substrate table. Thus, acontinuous flow of cleaning liquid through the immersion space may beused. The flushing process may be continued for any desired length oftime, but it is envisaged that flushing for, e.g., up to half an hour,for example 15 minutes, up to 10 minutes or even up to 5 minutes wouldbe sufficient to provide a cleaning effect. The cleaning liquid mayadditionally or alternatively be supplied to the immersion space andheld in the space for a period of time (e.g. up to 15 minutes, up to 10minutes or up to 5 minutes), before being flushed or pumped out. Thisprocess may be repeated one or more times.

Following cleaning, the immersion space may be rinsed with ultra-purewater. An advantage of one or more of the cleaning liquids describedherein is the ease of removing all traces of the cleaning liquid byrinsing with ultra-pure water. Thus, rinsing may be completed within,for example, half an hour.

The entire cleaning process may therefore be completed with a maximumdown-time of the apparatus of only an hour. Cleaning may therefore becarried out more frequently. Frequent cleaning has a benefit that acontamination level may be kept to a very low level at all times. Ifdesired, the cleaning process described herein may be carried out incombination with one or more less frequent cleaning processes which maybe off-line, such as mechanical spraying or mega-sonic cleaningtechniques. However, a benefit of the use of the cleaning process and/orcleaning liquid described herein is that the frequency of carrying outsuch an off-line cleaning method may be reduced or such an off-linetechnique may be eliminated entirely.

In an embodiment, cleaning may be carried out in the absence of asubstrate. This means that the substrate table WT is exposed to thecleaning liquid. As depicted in FIG. 1, only a part of the substratetable is normally part of the immersion space. In an embodiment, thesubstrate table may be moved while the cleaning liquid is within theimmersion space in order that different parts of the substrate table areexposed to the cleaning liquid. This may enable substantially the entiresubstrate table to be cleaned. The substrate table may be a source ofcontaminants for the immersion fluid. Cleaning without the presence of asubstrate may permit the substrate table to cross-contaminate othersurfaces of the immersion system. In an embodiment, the cleaning may bedone with the substrate in place on the substrate table, or with a dummysubstrate on the substrate table.

All the embodiments of the cleaning liquid supply system may have one ormore sensors to determine the concentration of the cleaner beingsupplied to the lithographic apparatus. The sensor may be located nearthe outlet 212 of the cleaning liquid supply system 200, or in theconduit that connects the cleaning liquid supply system 200 to thelithographic apparatus 1.

The cleaning liquid may pass through the liquid confinement structure inorder to remove contamination on a surface of the immersion space and/orother surface that comes into contact with the immersion fluid. Usedcleaning liquid, which may include a dissolved gas, may then flow out ofthe liquid confinement structure and into an outlet system, togetherwith, for example, the air contained in the liquid confinementstructure. The outlet fluid may then be passed through a separator whichseparates the liquid and gas phases. The gas phase may be released via agas bleed which is reached after the gas has passed through a charcoalfilter to remove ozone, if present. Other methods may be used to removeozone from the used cleaning liquid. For example, the ozone may beremoved as the gas phase passes under the illumination of a UV radiationdestructor lamp. The liquid phase may then pass through a degasser whichremoves dissolved ozone. Any appropriate type of degasser may be used,for example a membrane-based degasser, an aeration degasser or a columndegasser. The liquid that exits the degasser may then be drained.

As illustrated in FIG. 7, a drain switch 400 may be used to direct theflow of the liquid exiting the lithographic apparatus to at least one ofa plurality of different drains D1, D2. Although two drains areillustrated, additional drains may be used. The illustrated embodimentis not intended to be limiting in any way. The drain switch 400 may bein communication with the controller 240 and/or the controller 140. Thedrain switch 400 may include a manifold that has at least one inlet thatis in fluid communication with the lithographic apparatus, and outletsthat are each in fluid communication with the drains D1, D2,respectively. In the illustrated embodiment, the manifold is a three-wayvalve, but any suitable configuration may be used.

One of the drains D1 may further include a three-way valve or any othertype of manifold that may allow the user to direct the fluid to arecycle system or to a waste drain for disposal. Such a recycle systemmay be used to allow the fluid to be reused in the lithographicapparatus or in any other apparatus, either for cooling purposes or evenas an immersion liquid. Potential benefits of such a recycle system mayinclude reducing the cost to operate the lithographic apparatus byreducing downtime and improving the speed of operation. In addition, theinclusion of the drain switch 400 may avoid the presence of a cleaner ina normal liquid (e.g., water) drain. The other drain D2 may beconstructed and arranged to safely dispose of any liquid flowingtherethrough, including the cleaning liquid that has exited thelithographic apparatus. The drain D2 may be connected to a stripper orany other device that may further process the liquid prior to finaldisposal in a waste drain. In an embodiment, the two waste drains thatare illustrated in FIG. 7 may be the same waste drain.

By having the drain switch 400 in signal communication with thecontrollers 140, 240, the drains D1, D2 may be switched upon initiationof a cleaning sequence so that the cleaning liquid may flow to the drainD2 rather than the drain D1. Alternatively, or in addition, a sensor SDthat is in communication with the controllers 140, 240 may be located inbetween the outlet of the lithographic apparatus and the drain switch400. The sensor SD may be configured to detect whether there is cleanerin the liquid flowing to the drain switch 400 so that the drain switch400 may be switched to the appropriate configuration. Such aconfiguration may allow the liquid to flow to the appropriate drain forfurther handling. For example, if the liquid is to be recycled, acertain threshold for contaminants (e.g., cleaner) may be used todetermine whether the liquid is pure enough to be recycled. If theliquid contains contaminants above the threshold, the liquid may bedirected to the waste drain. The certain threshold may be apredetermined.

In an embodiment, the immersion lithographic system 100 may includemultiple drain switches that are in fluid communication with multipleoutlets of the lithographic apparatus and are in signal communicationwith the controller 140. Such an arrangement may allow other fluids thatare used in the lithographic apparatus, such as a cooling fluid, to bedirected to the appropriate drain, which may be defined by the user.

As illustrated in FIG. 9, the immersion lithographic system 100 mayinclude a switch 150 that is constructed and arranged to allow thecleaning liquid to by-pass at least a portion of a liquid purificationsystem 155 of the lithographic apparatus 1. In the illustratedembodiment, the liquid purification system 155 includes a heat exchanger160 and a particle filter 170. The liquid purification system 155 mayalso include at least one degassing unit (not shown) that is configuredto decrease the dissolved gas content of the liquid flowingtherethrough. The heat exchanger 160 and particle filter 170 typicallyhave relatively large volumes and provide for a relatively low flowvelocity, which may make it difficult to flush chemicals therethrough.It is desirable to flush the cleaning liquid out of the lithographicapparatus 1 prior to operating the lithographic apparatus 1 in anexposure mode.

In order to reduce or minimize the duration of time it takes to flushthe cleaning liquid out of the lithographic apparatus 1, it is desirableto prevent the cleaning liquid to pass through the heat exchanger 160and the particle filter 170. The controller 140 may be configured toprovide a signal to the switch 150 to direct the flow of the cleaningliquid to a by-pass 180 when a cleaning mode has been initiated by thecontroller 240 of the cleaning liquid supply system 200. The switch 150may be in the form of a three-way valve, as illustrated, or may be anyother type of suitable manifold. A valve 190, such as a three-way valve,may be provided at the end of the by-pass 180 to rejoin the flow pathwith a path that exits the by-passed portion of the liquid purificationsystem 155. The cleaning liquid may then flow to other parts of thelithographic apparatus, such as the liquid confinement structure IH. Atthe end of the cleaning mode, the same flow path, i.e. through theby-pass 180, may be flushed with a fluid that does not include acleaner, such as the immersion liquid, or any other suitable fluid.

FIG. 10 illustrates an embodiment of an immersion lithographic system500 that is constructed and arranged to deliver the cleaning liquid fromthe cleaning liquid supply system 200 to a location within thelithographic apparatus 1 that is closer in proximity to the liquidconfinement structure IH, as compared to the embodiments of theimmersion lithographic system 100 illustrated in FIGS. 7 and 9. Asillustrated, the cleaning liquid supply system 200 may include a flowcontrol device 550 that is constructed and arranged to control the flowof the liquid entering the inlet 210 and whether the liquid entering theinlet 210 flows into the mixer 232 or bypasses the mixer 232 via aby-pass 516. In an embodiment, the flow control device 550 may not bepart of the cleaning liquid supply system by may be part of the liquidsupply system 300, or may be located in between the liquid supply system300 and the cleaning liquid supply system 200.

The flow control device 550 may include a three-way valve, a pump, orany other device that may control the amount and/or direction of flow ofthe liquid entering the cleaning liquid supply system 200. The flowcontrol device 550 may be in signal communication with the controller240 (discussed above) so that the controller 240 may control the flow ofthe liquid entering the cleaning liquid supply system 200. For example,if the lithographic apparatus 1 is to operate under exposure conditions,the controller 240 may provide a signal to the flow control device 550so that the mixer 232 may be by-passed and the liquid may be provided tothe lithographic apparatus 1 without any cleaner mixed therein.

As illustrated in FIG. 10, the by-pass 516 extends from the flow controldevice 550 to the liquid purification system 155, the details of whichare discussed above. Thus, the by-pass 516 is configured to by-pass thecleaning liquid supply system 200 such that the by-pass 516 cannot becontaminated with cleaners from the cleaning liquid supply system 200. Aseparate conduit 512 extends from the mixer 232 in the cleaning liquidsupply system 200 to a flow control device 530 that is locateddownstream from the liquid purification system 155. Desirably, the flowcontrol device 530 is located in close proximity to the liquidconfinement structure IH in the lithographic apparatus 1 so that theamount of time that is needed to flush the cleaning liquid out of theliquid confinement structure IH may be reduced, as discussed in furtherdetail below.

As illustrated, another flow control device 540 is located between theflow control device 530 and the liquid confinement structure IH and isconfigured to direct the flow of the liquid passing therethrough to theliquid confinement structure IH or to a drain switch 560 via a conduit552. The drain switch 560 may be a three way valve, or any other type offlow control device that can direct the flow of a liquid entering thedrain switch to the recycle system or to the waste drain, as discussedabove.

In operation, when the immersion lithographic apparatus is exposing asubstrate, the flow control device 550 may be configured to direct theliquid received from the liquid supply system 300 via the inlet 210 tothe liquid purification system 155 via the by-pass 516. After the liquidhas passed through the liquid purification system, it may flow throughthe flow control devices 530, 540 and to the liquid confinementstructure IH. If desired, the flow control device 540 may be switched sothat the liquid may flow to the drain switch 560 rather than to theliquid confinement system IH. If the liquid has not been contaminated,it may be directed to the recycle system, but if contamination has beendetected in the liquid, the liquid may be directed to the waste drain.

When it is desired to clean the liquid confinement system IH, the flowcontrol device 550 is signaled to direct the liquid received from theliquid supply system 300 via the inlet 210 to the mixer 232, where oneof more of the cleaning agents discussed above may be mixed with theliquid, as discussed above. The resulting cleaning liquid may then flowdirectly to the flow control device 530, through the flow control device540 and to the liquid confinement system IH. Upon completion of acleaning cycle, the flow control device 530 may block the flow ofcleaning liquid from the conduit 512 and may allow the liquid from theliquid purification system 155 to flush any remaining cleaning liquidout of the lithographic apparatus 1. At about the same time, the flowcontrol device 550 may switch the direction of the liquid flowing thoughthe inlet 210 to enter the by-pass 516 rather than the mixer 232. Theflow control device 540 and drain switch 560 may also be controlled toallow any liquid having traces of the cleaners to be directed to thewaste drain.

By allowing the liquid from the liquid supply system 300 to flow througha separate conduit 516 to the lithographic apparatus 1, rather than thesame conduit 512 that is used to deliver the cleaning fluid to theimmersion lithographic apparatus 1, the amount of time it takes to flushthe cleaning fluid out of the immersion lithographic apparatus 1 may bereduced.

Features of each of the embodiments herein may be combined with featuresof one or more of the other embodiments, as appropriate.

In a first aspect, there is provided an immersion type lithographicapparatus comprising an immersion system configured to at leastpartially fill an immersion space with an immersion liquid, an indicatorconfigured to indicate whether a part of the lithographic apparatusshould be cleaned, and a cleaning liquid supply system configured tosupply a cleaning liquid comprising a cleaner to the part of thelithographic apparatus, the cleaner being at least one of a plurality ofdifferent cleaners, each cleaner or combination of cleaners beingconfigured to clean a different type and/or level of contamination inthe part of the lithographic apparatus, and a controller configured tocontrol which of the plurality of cleaners is provided to the part ofthe lithographic apparatus, based on an indication received from theindicator. Optionally, the immersion type lithographic apparatus furthercomprises an in-line cleaning cabinet, wherein the plurality ofdifferent cleaners and the controller are located within the in-linecleaning cabinet. Desirably, the immersion type lithographic apparatusis configured such that the immersion liquid passes through the in-linecleaning cabinet prior to partially filling the immersion space.Optionally, one of the plurality of different cleaners compriseshydrogen peroxide. Optionally, one of the plurality of differentcleaners comprises ozone. Desirably, the cleaner supplied is peroxone.Optionally, one of the plurality of different cleaners comprises atleast one selected from the group consisting of: a soap, an alkalicfluid, an acid, and a solvent. Desirably, one of the plurality ofdifferent cleaners comprises a soap. Desirably, one of the plurality ofdifferent cleaners comprises at least one solvent selected from one ormore glycol ethers, esters, alcohols, and ketones. Optionally, one ofthe plurality of different cleaners comprises diethylene glycolmonobutyl ether and/or ethoxylated secondary C12-14-alcohol. Optionally,the indicator comprises at least one selected from the group consistingof: i) an exposure counter configured to count a number of substratesexposed since a previous cleaning action; ii) a timer configured to timethe duration since a previous cleaning action; iii) a particle counterconfigured to count a number of contaminant particles that have exitedthe immersion system over a certain amount of time; and iv) a sensorconfigured to sense a certain level of contamination in the lithographicapparatus. Optionally, the immersion type lithographic apparatus furthercomprises a first drain configured to receive the immersion liquid fromthe immersion system, a second drain configured to receive the cleaningliquid, and a switch configured to direct liquid flowing out of theimmersion system to the first drain or the second drain depending onwhether the immersion liquid or the cleaning liquid is flowing out ofthe immersion system. Desirably, the first drain is connected to animmersion liquid recycle system configured to purify the immersionliquid for reuse in the immersion system.

In a second aspect, there is provided an in-line cleaning cabinet for animmersion type lithographic apparatus, the in-line cleaning cabinetcomprising a fluid outlet constructed and arranged to provide a cleaningfluid to the immersion type lithographic apparatus, a plurality ofcleaner supply devices in fluid communication with the fluid outlet,each of the cleaner supply devices being constructed and arranged tosupply a cleaner to the fluid outlet, and a controller configured tocontrol the plurality of cleaner supply devices based on a level and/ortype of contamination within the immersion type lithographic apparatusso that the cleaning fluid comprises at least one of the cleaners.Optionally, the in-line cleaning cabinet further comprises a fluid inletconstructed and arranged to receive an immersion fluid to be used in theimmersion type lithographic apparatus, the fluid inlet being in fluidcommunication with the fluid outlet, and a mixer in fluid communicationwith the fluid inlet, the plurality of cleaner supply devices, and thefluid outlet, the mixer being constructed and arranged to mix at leastone of the cleaners with the immersion fluid, wherein the mixer is insignal communication with the controller. Desirably, the immersion fluidcomprises ultra pure water. Optionally, the controller is configured tocommunicate with a controller of the immersion type lithographicapparatus. Desirably, the controller of the in-line cleaning cabinet isconfigured to prevent the cleaning fluid from flowing out of the fluidoutlet when an exposure is taking place within the immersion typelithographic apparatus. Optionally, at least one of the cleanerscomprises hydrogen peroxide. Desirably, the in-line cleaning cabinetfurther comprises a storage container for the hydrogen peroxide.Optionally, least one of the cleaners comprises ozone. Desirably, thein-line cleaning cabinet further comprises an ozone generator.Optionally, at least one of the cleaners comprises diethylene glycolmonobutyl ether and/or ethoxylated secondary C12-14-alcohol. Optionally,the controller is configured to communicate with a contaminationindicator in the immersion type lithographic apparatus, and wherein thecontamination indicator is configured to detect the level and/or type ofcontamination within the immersion type lithographic apparatus.

In a third aspect, there is provided a method of cleaning an immersiontype lithographic apparatus, the method comprising sensing contaminationwithin the immersion type lithographic apparatus, selecting a cleaningmode from a plurality of cleaning modes in response to the sensing, andproviding a cleaner from a cleaning system to the contaminated part ofthe immersion type lithographic apparatus based on the selected cleaningmode. Optionally, each of the plurality of cleaning modes corresponds toa different cleaner. Optionally, the selecting is based on the typeand/or level of sensed contamination. Optionally, the cleaner providedin one of the plurality of cleaning modes comprises hydrogen peroxide.Desirably, the cleaner provided in one of the plurality of cleaningmodes comprises peroxone. Optionally, the cleaner provided in one of theplurality of cleaning modes comprises at least one selected from thegroup consisting of: ozone, an alkaline, a soap, and an acid. Desirably,one of the plurality of different cleaners comprises a soap. Desirably,one of the plurality of different cleaners comprises at least onesolvent selected from one or more glycol ethers, esters, alcohols, andketones. Optionally, the cleaner provided in one of the plurality ofcleaning modes comprises diethylene glycol monobutyl ether and/orethoxylated secondary C12-14-alcohol. Optionally, the method furthercomprises switching a drain switch from one position to another positionso that the cleaner flows out of the immersion type lithographicapparatus to one of a plurality of drains. Optionally, the cleaningsystem is located in an in-line cleaning cabinet, the in-line cleaningcabinet being in fluid communication with the immersion typelithographic apparatus. Optionally, the method further comprises mixingthe cleaner with a fluid being provided to the immersion typelithographic apparatus. Desirably, the fluid comprises ultra pure water.

In a fourth aspect, there is provided a method for supplying a cleaningfluid from an in-line cleaning cabinet to an immersion type lithographicapparatus, the method comprising supplying a first cleaner to thein-line cleaning cabinet, supplying a second cleaner to the in-linecleaning cabinet, detecting an amount and/or type of contaminationwithin the immersion type lithographic apparatus, determining a ratio ofthe first cleaner and the second cleaner to mix with a fluid carrierbased on the detecting, and supplying a mixture of the fluid carrier andthe first cleaner and/or the second cleaner to the immersion typelithographic apparatus. Optionally, the method further comprisessupplying the fluid carrier to the in-line cleaning cabinet. Optionally,the method further comprises controlling when the mixture is supplied tothe immersion type lithographic apparatus based on operation of theimmersion type lithographic apparatus. Desirably, the method furthercomprises preventing the mixture from being supplied to the immersiontype lithographic apparatus when an exposure operation is taking placein the immersion type lithographic apparatus. Optionally, the methodfurther comprises mixing the first cleaner and/or the second cleanerwith the fluid carrier. Desirably, the first cleaner comprises hydrogenperoxide, and wherein the mixing comprises mixing the hydrogen peroxidewith the fluid carrier so that the mixture comprises about 1% of thehydrogen peroxide. Desirably, the first cleaner comprises hydrogenperoxide and the second cleaner comprises ozone, and wherein the mixingcomprises mixing the hydrogen peroxide and the ozone so that the mixturecomprises between about 3 ppm and about 5 ppm hydrogen peroxide andabout 10 ppm ozone. Desirably, the supplying the second cleanercomprises generating the ozone. Optionally, the fluid carrier comprisesultra pure water. Optionally, the method further comprises selecting acleaning mode from a plurality of cleaning modes based on the detecting,wherein the ratio is determined based on the selected cleaning mode.

In a fifth aspect, there is provided an immersion type lithographicsystem, comprising an immersion type lithographic apparatus, comprisinga support constructed and arranged to support a substrate, a projectionsystem constructed and arranged to project a patterned beam of radiationonto a target portion of the substrate, and a liquid confinementstructure configured to at least partially fill a space between theprojection system and the substrate and/or support with a liquid, aliquid supply system constructed and arranged to supply the liquid tothe liquid confinement structure, and a cleaning system constructed andarranged to supply a cleaner to the immersion type lithographicapparatus, the cleaning system being in fluid communication with theliquid supply system and the liquid confinement structure. Optionally,the cleaning system comprises a plurality of different cleaners, eachcleaner or combination of cleaners being configured to clean a differenttype and/or level of contamination in the part of the lithographicapparatus, and a controller configured to control which of the pluralityof cleaners is provided to the lithographic apparatus, based on inputreceived from a sensor. Desirably, one of the plurality of differentcleaners comprises hydrogen peroxide. Desirably, one of the plurality ofdifferent cleaners comprises ozone. Desirably, one of the plurality ofdifferent cleaners comprises at least one selected from the groupconsisting of: a soap, an alkalic fluid, an acid, and a solvent.Desirably, one of the plurality of different cleaners comprises a soap.Desirably, one of the plurality of different cleaners comprises at leastone solvent selected from one or more glycol ethers, esters, alcohols,and ketones. Desirably, one of the plurality of different cleanerscomprises diethylene glycol monobutyl ether and/or ethoxylated secondaryC12-14-alcohol. Optionally, the cleaning system comprises an in-linecleaning cabinet. Desirably, the in-line cleaning cabinet comprises afluid outlet constructed and arranged to provide a cleaning fluidcomprising the cleaner to the immersion type lithographic apparatus, aplurality of cleaner supply devices in fluid communication with thefluid outlet, each of the cleaner supply devices being constructed andarranged to supply a cleaner to the fluid outlet, and a controllerconfigured to control the plurality of cleaner supply devices based on alevel and/or type of contamination within the immersion typelithographic apparatus so that the cleaning fluid comprises at least oneof the cleaners from the plurality of cleaner supply devices.Optionally, the immersion type lithographic system further comprises anenclosure, wherein the liquid supply system and the cleaning system arelocated within the enclosure. Optionally, the immersion typelithographic system further comprises an enclosure, wherein the cleaningsystem and the immersion type lithographic apparatus are located withinthe enclosure.

In a sixth aspect, there is provided an immersion type lithographicapparatus comprising a support constructed and arranged to support asubstrate, a projection system constructed and arranged to project apatterned beam of radiation onto a target portion of the substrate, animmersion system configured to at least partially fill a space betweenthe projection system and the substrate and/or support with an immersionliquid, a contamination indicator constructed and arranged to generate asignal that initiates a cleaning sequence configured to clean at least apart of the lithographic apparatus, and a cleaning liquid supply systemconfigured to provide a cleaning liquid to the part of the lithographicapparatus, the cleaning liquid supply system comprising a plurality ofdifferent cleaners, each cleaner or combination of cleaners beingconfigured to clean a different type and/or level of contamination inthe part of the lithographic apparatus. Optionally, the indicatorcomprises at least one selected from the group consisting of: i) anexposure counter configured to count a number of substrates exposedsince a previous cleaning action; ii) a timer configured to time theduration since a previous cleaning action; iii) a particle counterconfigured to count a number of contaminant particles that have exitedthe immersion system over a certain amount of time; and iv) a sensorconfigured to sense a certain level of contamination in the lithographicapparatus. Optionally, the immersion type lithographic apparatus furthercomprises a first drain configured to receive the immersion liquid fromthe immersion system, a second drain configured to receive the cleaningliquid provided during a cleaning sequence, and a switch configured todirect liquid flowing out of the immersion system to the first drain orthe second drain depending on whether the immersion liquid or thecleaning liquid is flowing out of the immersion system. Desirably, thefirst drain is connected to an immersion liquid recycle systemconfigured to purify the immersion liquid for reuse in the immersionsystem.

In a seventh aspect, there is provided an immersion type lithographicsystem comprising a support constructed and arranged to support asubstrate, a projection system constructed and arranged to project apatterned beam of radiation onto a target portion of the substrate, animmersion system configured to at least partially fill a space betweenthe projection system and the substrate and/or support with a liquid, acleaning liquid supply system configured to provide a cleaning liquid toa part of the lithographic apparatus, and a drain switch constructed andarranged to direct the immersion liquid to a first drain, and thecleaning liquid to a second drain depending on whether the immersionliquid or the cleaning liquid is flowing out of the immersion system.

In an eighth aspect, there is provided an immersion type lithographicapparatus comprising a support constructed and arranged to support asubstrate, a projection system constructed and arranged to project apatterned beam of radiation onto a target portion of the substrate, animmersion system configured to at least partially fill a space betweenthe projection system and the substrate and/or support with an immersionliquid, a cleaning liquid supply system configured to provide a cleaningliquid to a part of the lithographic apparatus, and a switch constructedand arranged to direct the immersion liquid through a liquidpurification system and to direct the cleaning liquid to by-pass atleast a portion of the liquid purification system. Optionally, theportion of the purification system comprises a heat exchanger.Optionally, the portion of the purification system comprises a particlefilter.

In a ninth aspect, there is provided an immersion type lithographicapparatus comprising a support constructed and arranged to support asubstrate, a projection system constructed and arranged to project apatterned beam of radiation onto a target portion of the substrate, animmersion system configured to at least partially fill a space betweenthe projection system and the substrate and/or support with an immersionliquid, a cleaning liquid supply system configured to provide a cleaningliquid to a part of the lithographic apparatus via a first conduit, anda switch constructed and arranged to direct the immersion liquiddirectly to a liquid purification system via a second conduit that isseparate from the first conduit and to direct the immersion liquidthrough the cleaning liquid supply system.

In a tenth aspect, there is provided a method of cleaning an immersiontype lithographic apparatus, the method comprising sensing contaminationwithin the immersion type lithographic apparatus, providing a cleanerfrom a cleaning system to the immersion type lithographic apparatus,bypassing at least a portion of a liquid purification system within thelithographic apparatus with the cleaner, and cleaning a part of theimmersion type lithographic apparatus with the cleaner. Optionally,bypassing comprises bypassing a heat exchanger. Optionally, thebypassing comprises bypassing a particle filter.

In accordance with embodiments of the invention, there is provided animmersion type lithographic apparatus that includes an indicator. Theindicator may include at least one selected from the group consistingof: i) an exposure counter configured to count a number of substratesexposed since a previous cleaning action; ii) a timer configured to timethe duration since a previous cleaning action; iii) a particle counterconfigured to count a number of contaminant particles that have exitedthe immersion system over a certain amount of time; and iv) a sensorconfigured to sense a certain level of contamination in the lithographicapparatus.

In accordance with an embodiment of the invention, there is provided animmersion type lithographic apparatus that includes an immersion systemthat is configured to at least partially fill an immersion space with animmersion liquid. A drain is connected to an immersion liquid recyclesystem that is configured to purify the immersion liquid for reuse inthe immersion system.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm).

The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, including refractiveand reflective optical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the embodiments of the invention maytake the form of a computer program containing one or more sequences ofmachine-readable instructions describing a method as disclosed above, ora data storage medium (e.g. semiconductor memory, magnetic or opticaldisk) having such a computer program stored therein. Further, themachine readable instruction may be embodied in two or more computerprograms. The two or more computer programs may be stored on one or moredifferent memories and/or data storage media.

The controllers described above may have any suitable configuration forreceiving, processing, and sending signals. For example, each controllermay include one or more processors for executing the computer programsthat include machine-readable instructions for the methods describedabove. The controllers may also include data storage medium for storingsuch computer programs, and/or hardware to receive such medium.

One or more embodiments of the invention may be applied to any immersionlithography apparatus, in particular, but not exclusively, those typesmentioned above and whether the immersion liquid is provided in the formof a bath or only on a localized surface area of the substrate, or isunconfined. In an unconfined arrangement, the immersion liquid may flowover the surface of the substrate and/or substrate table so thatsubstantially the entire uncovered surface of the substrate table and/orsubstrate is wetted. In such an unconfined immersion system, the liquidsupply system may not confine the immersion liquid or it may provide aproportion of immersion liquid confinement, but not substantiallycomplete confinement of the immersion liquid.

An immersion system as contemplated herein should be broadly construed.In certain embodiments, it may be a mechanism or combination ofstructures that provides a liquid to a space between the projectionsystem and the substrate and/or substrate table. It may comprise acombination of one or more structures, one or more liquid inlets, one ormore gas inlets, one or more gas outlets, and/or one or more liquidoutlets that provide liquid to the space. In an embodiment, a surface ofthe space may be a portion of the substrate and/or substrate table, or asurface of the space may completely cover a surface of the substrateand/or substrate table, or the space may envelop the substrate and/orsubstrate table. The immersion system may optionally further include oneor more elements to control the position, quantity, quality, shape, flowrate or any other feature of the liquid. The one or more controllingelements can be provided to control the apparatus. The controller mayhave a processor which may operate to execute the one or more computerprograms.

The immersion liquid used in the apparatus may have differentcompositions, according to the desired properties and the wavelength ofexposure radiation used. For an exposure wavelength of 193 nm, ultrapure water or water-based compositions may be used and for this reasonthe immersion liquid is sometimes referred to as water and water-relatedterms such as hydrophilic, hydrophobic, humidity, etc. may be used,although they should be considered more generically. It is intended thatsuch terms should also extend to other high refractive index liquidswhich may be used, such as fluorine containing hydrocarbons.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

What is claimed is:
 1. An immersion type lithographic system,comprising: an immersion type lithographic apparatus, comprising: asupport constructed and arranged to support a substrate, a projectionsystem constructed and arranged to project a patterned beam of radiationonto a target portion of the substrate, and a liquid confinementstructure configured to at least partially fill a space between theprojection system and the substrate and/or support with an immersionliquid; a liquid supply system constructed and arranged to supply theimmersion liquid to the liquid confinement structure; and a cleaningsystem constructed and arranged to supply a cleaning liquid comprising acleaner to a part of the liquid confinement structure to clean the partof the liquid confinement structure, the cleaning system furthercomprising an outlet system configured and arranged to receive a usedcleaning liquid and the cleaning system further configured to select acleaning mode from a plurality of cleaning modes and provide the cleanerfrom a plurality of different cleaners to the part of the liquidconfinement structure based on the selected cleaning mode.
 2. Theimmersion type lithographic system according to claim 1, wherein theliquid confinement structure is configured such that the cleaning liquidpasses through the liquid confinement structure.
 3. The immersion typelithographic system according to claim 1, wherein the part is a bottomsurface of the liquid confinement structure.
 4. The immersion typelithographic system according to claim 1, wherein the part is a microsieve provided in the bottom surface.
 5. The immersion type lithographicsystem according to claim 1, wherein the cleaning system is constructedand arranged to supply ultra-pure water to the part of the liquidconfinement structure to rinse the part of the liquid confinementstructure after cleaning the part of the liquid confinement structure.6. The immersion type lithographic system according to claim 1, whereinthe outlet system comprises a separator configured to separate liquidand gas phases included in the used cleaning liquid.
 7. The immersiontype lithographic system according to claim 6, wherein the outlet systemcomprises a degasser to remove the gas from the cleaning liquid, theoutlet system further comprising a drain configured to receive a liquidexiting the degasser.
 8. The immersion type lithographic systemaccording to claim 7, further comprising a recycle system and a drainswitch to direct the liquid exiting the degasser to the recycle systemor to a waste drain for removal.
 9. The immersion type lithographicsystem according to claim 8, wherein the recycle system is configured topurify the liquid for reuse as immersion liquid by the liquid supplysystem.
 10. The immersion type lithographic system according to claim 1,wherein the lithographic apparatus further comprises an indicatorconfigured to indicate whether the part of the lithographic apparatusshould be cleaned.
 11. The immersion type lithographic system accordingto claim 10, wherein the indicator comprises at least one selected fromthe group consisting of: i) an exposure counter configured to count anumber of substrates exposed since a previous cleaning action; ii) atimer configured to time the duration since a previous cleaning action;iii) a particle counter configured to count a number of contaminantparticles that have exited the immersion system over a certain amount oftime; and iv) a sensor configured to sense a certain level ofcontamination in the lithographic apparatus.
 12. The immersion typelithographic system according to claim 1, wherein the cleaner comprisesan alkali fluid.
 13. The immersion type lithographic system according toclaim 1, the cleaning system being in fluid communication with theliquid supply system and the liquid confinement structure.
 14. A methodof cleaning an immersion type lithographic apparatus, the methodcomprising: receiving an indication that a part of a liquid confinementstructure of the immersion type lithographic apparatus should becleaned; selecting a cleaning mode from among a plurality of differentcleaning modes based on the indication; providing a cleaning liquidcomprising a cleaner selected based on the cleaning mode, from acleaning system to the part of the liquid confinement structure of theimmersion type lithographic apparatus to clean the part of the liquidconfinement structure; and providing a rinsing liquid to the part of theimmersion type lithographic apparatus to rinse the part.
 15. The methodaccording to claim 14, wherein the rinsing liquid comprises ultra-purewater.
 16. The method according to claim 14, wherein the cleanercomprises at least one selected from the group consisting of: ozone, analkaline, a soap, and an acid.
 17. The method according to claim 14,wherein the cleaning system is located in an in-line cleaning cabinet,the in-line cleaning cabinet being in fluid communication with theimmersion type lithographic apparatus.
 18. The method according to claim14, further comprising providing a used cleaning liquid, the usedcleaning liquid being the cleaning liquid provided to clean the part, toan outlet system.
 19. The method according to claim 18, furthercomprising removing ozone from the used cleaning liquid using a degasserof the outlet system.
 20. The method according to claim 19, furthercomprising directing a liquid exiting the degasser to a recycle systemfor reuse in the lithographic apparatus or to a waste drain for removal.21. An immersion type lithographic system, comprising: a supportconstructed and arranged to support a substrate; a projection systemconstructed and arranged to project a patterned beam of radiation onto atarget portion of the substrate; and a liquid confinement structureconfigured to at least partially fill a space between the projectionsystem and the substrate and/or support with an immersion liquid; aliquid supply system constructed and arranged to supply the immersionliquid to the liquid confinement structure; an indicator configured toprovide a signal to indicate whether a part of the lithographicapparatus should be cleaned; and a cleaning system constructed andarranged to supply a cleaning liquid comprising a cleaner to a part ofthe liquid confinement structure to clean the part of the liquidconfinement structure, the cleaning system further constructed andarranged to select among a plurality of different cleaning modes usingthe cleaning liquid based on the signal.
 22. The immersion typelithographic system according to claim 21, wherein the cleaning systemis constructed and arranged to provide the cleaner from a plurality ofdifferent cleaners to the part of the liquid confinement structure basedon the selected cleaning mode.